A method is disclosed for determining attenuation values for PET data of a patient. In at least one embodiment, the method includes detecting at least one accessory of a magnetic resonance imaging scanner and detecting the position and/or alignment of the accessory by way of an imaging measuring method； comparing the detected accessory with data from a database； and assigning an attenuation map, which is contained in the database, to attenuation values of the detected accessory and adapting the attenuation map to the detected position and/or alignment of the accessory.
